different categories of chest pain

stable angina: narrowing of vessel caliper causes decreased blood supply down stream. This is exacerbated when demand exceeds supply (e.g. exercise). There is no cardiac injury (negative troponins).
unstable angina: very rare category now with high sensitivity troponin. Can have normal EKG. Vessel is not occluded, still with some blood flow.
NSTEMI: same process as unstable angina but now with cell necrosis and troponin elevation. Complete occlusion with no blood flow.
STEMI: all tissues downstream are ischemic and can lead to necrosis. Troponin will eventually become positive but don’t wait for it.

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